Tuesday, April 19, 2011

Why you should avoid airline tea but coffee is okay

To make tea, the water needs to be near to 100 C. But on a plane water boils at too low a temperature, so you'll never get a decent brew.

It's because although airline cabins are pressurised, the pressure is significantly below normal sea-level atmospheric pressure.  And it's the ambient pressure that determines the temperature at which water boils. At normal sea-level atmospheric pressure, it's 100 C. At lower pressures, the boiling point is lower.

It follows that you should make a better cup of tea in fine weather (high pressure) than in a storm (low pressure). Has anyone actually noticed this? I haven't, but now the thought has occurred to me, I intend to check.

And it presumably means that in Tibet, too, tea is a bit substandard. Which is a shame. For I remember a book I had when I was little which said that tea is a traditional drink for Tibetans, and it’s taken with rancid butter.

The low boiling point of water on board an aircraft should pose less of a problem when you're brewing coffee, which is best made with water at 95 C.

There’s a vital figure missing from the foregoing, namely at what temperature water does in fact boil on a normal airliner.  Sadly I can't supply this.  You’ll need to read In-flight Science, by Brian Clegg, Icon Books, £12.99, reviewed in New Scientist on 9th April.

1 comment:

  1. Good point about the Tibetans! And making tea in fine weather. I think it tastes better because I need it more - but there could be more to it than this!